Surgical or medical wires and cables are used in a variety of surgical procedures, for example, reconstructive spine surgery such as fusions, spinal trauma surgery, total hip arthroplasty, fracture fixation, open heart surgery for closures of the sternum, oral and facial surgery to fix mandibular fractures and the like, and other surgical procedures. Often, medical cables and wires are used to encircle or loop about bones to hold them together for healing or fusion in some types of spinal surgery. For purposes of this application, "cable" includes monofilament and single strand wire along with multi-filament and multi-strand cable and wire ropes.
In some surgical procedures, it is desirable to provide a tensile force to selected portions of the patient's body such as to adjacent vertebrae. This may be accomplished by placing loops formed of medical cable about the vertebrae. In placing the loops around the vertebrae with the desired tension on the vertebrae, it is frequently necessary to pass the cables sublaminarly, to apply the desired tension on the vertebrae through the cables, and then secure the cables in loops. One method of accomplishing these tasks is for the surgeon to pass a suture sublaminarly, to secure the suture to a mid-section of the cable, pull the suture with the attached cable back under the lamina of the vertebrae, and then cut the suture and cable so that two cables exist under the lamina of the patient. The cables can then be looped about the vertebrae and tightened by hand with the surgeon plucking the cables to determine the tension. After pulling the cables until the surgeon determines that the desired tension is applied, the surgeon attempts to secure the cables in their respective loops while maintaining the tension thereon.
Problems sometime occur with placing the correct tension on the medical cables during installation. Conventional systems for attaching medical cables to selected portions of the patient's body have experienced problems with the cables being applied too tightly and creating vascular necrosis of the bone around the cables. At the same time, medical cables must be tight enough to achieve the desired mechanical fixation. Many conventional systems are difficult to manipulate and surgeons have experienced problems in properly positioning the cables while at the same time applying the desired tension and then securing the cables in the loops with that desired tension still applied. Many currently available tensioner products do not provide direct feedback to a surgeon concerning the amount of tension being applied to the cable. Securing the cables in their respective loops with conventional products and methods has also involved problems.
One method for securing the cables in their respective loops has been to provide a permanent loop on one end of the cables. This method involves forming a small loop on one end of the cable and securing the small loop with a crimp, and then passing the end opposite the small loop through the small loop in an arrangement similar to a cowboy's lasso. Then a crimp member with a flange may be placed on the cable opposite the small loop and slid along the cable until snug against the small loop member. Then after applying the desired tension as accurately as possible with conventional systems, the surgeon attempted to crimp the crimp member while maintaining the desired tension so that a secured loop is formed with the desired tension. This method involves two crimp members and has two parts of the cables resting against each other which may lead to increased wear of the cable and increased likelihood of premature failure. Additionally, it may be difficult to accurately maintain the tension on the cable while the cables are crimped.
Another method for securing the cable is to provide bar member with two transverse apertures. A stop member is attached to one end of the cable and then the other cable end is passed through one of the apertures until a stop rests against the bar member. The cable end opposite the stop member forms a loop and is then passed through the other aperture and then through a crimp member. The crimp member is placed snugly against the bar member and crimped while the surgeon attempts to maintain the desired tension on the cable. Among the shortcomings of this method may be the difficulty in holding all the parts with surgical instruments during this procedure. Additionally, this method and the previously described method do not protect against fraying once the cable is cut. See U.S. Pat. No. 5,116,340, which is incorporated by reference for all purposes.
Therefore, a need has arisen for a surgical installation system and apparatus that efficiently secure a medical cable in a loop, uses a small number of parts, is easily handled by a minimum number of surgical instruments, does not allow the cable to rest against other portions of the cable, helps prevent fraying, and helps to assure that the desired tension is produced in the secured loop.